Re:Using Threads and Application.processMessage to Cancel operationof main thread.
Robert,
I do not wish to do my main processing in a child thread.
I prefer keeping it in VCL's main thread.
Can I not do this ?
The reason behind this is that my main procedure is not a single method and
it is not even a simple loop.
It is a sequence of functions which are coded in different libraries and are
interdependent. some of them actually wait for the other to finish.
For example, whenever I do database access, I use a SendAndWait.
Which means that I am using a blocking socket. The program execution waits
till sendAndWait finishes. Dependeding on it's result, I change and call
various other functions.
Hence I would prefer keeping it in same main VCL thread. I just want to get
the Application.ProcessMEssages in a different thread so that my app can
somehow process those messages.
Rgds
Amit
Quote
Robert Cerny <robert.qwe.ce...@neosys.xrs.qwe.si> wrote in message
news:a23qoo.4s8.1@neosys.xrs.si...
Quote
> VCL message loop runs in main thread. This means that you have to leave
main
> thread to process user messages and create additional "working" threads:
> procedure TWorkThread.Execute;
> begin
> while Have_Some_Job and not Canceled do
> {do your job}
> end;
> procedure Txx.CancelBtnClick();
> begin
> Canceled := true;
> end;
> procedure Txx.StartBtnClick();
> begin
> TWorkThread.Create(false);
> CancelBtn.Enabled := true;
> end;
> --
> Robert
> Amit wrote in message <3c44fb89_2@dnews>...
> >HI,
> >I have a problem with using threads.
> >Problem :
> >How can I use VCLs main thread to listen to windows messages posted in
> >message queue of a child thread.
> >I need to run a main form in which I perform repeated database access.
> >Mine is a three tier application hence the data-access may be time
> >consuming.
> >I want to provide a cancel button, using which the user may cancel
current
> >activity.
> >Basically I will use a GlobalFlag which will be set once the cancel
button
> >is pressed.
> >Each function in my main form, checks for the value of this flag before
> >proceeding.
> >My problem is that I am not able to trap the cancel button click.
> >I tried creating a separate child thread with Execute method looking like
> :
> >TCancelThread.Execute;
> >begin
> > while(True) do
> > Application.ProcessMessages;
> >end;
> >but it does not trap.
> >I also tried to create a separate form for cancel button. I showed it
with
> >formStyle : fsStayOnTop, and disabled the main form. still it did not
trap
> >the message.
> >How can I trap ONLY Cancel Button Click while my main thread continues
it's
> >work.
> >Rgds
> >Amit
